Sorry I don't have the answer... But I thought I would post to say I think you are describing normal OCD. You say that most people have a compulsion to do something to stop 'something' happening eg washing hands otherwise you'll die of germs. Yours sounds the same but it's an absence if something. Ie I must stop playing the guitar or I will ejaculate... For you it's stopping the action which in itself is still an action. Unfortunately I suppose because many things can trigger your action (or non action) it must affect you a great deal. I know the answer lies in believing that you/your mind/brain controls your body and not the other way round. I'm sorry to say I don't know how to get that belief. I had a problem where I couldn't swallow. Food drink or anything I had to cut into tiny pieces and I believed vehemently that I did not have control of my throat. And because I believed it it was true. The flap at the back of my mouth would not close so food would always go down the wrong hole and as a self fulfilling prophesy I choked often further increasing my fear. And I knew it was mental as when I got drunk I was fine... In fact I could only eat anything when I was hammered. And panic attacks are the same... You believe you can't breathe unless you get out where you are. Your situation almost sounds like a panic attack albeit unusually manifested. Try and figure out how to control your brain. Meditation? You can listen to brain entraining binaural beats (that's what I'm trying at the mo dunno if it works but hey) or nlp? The thing with therapy is they try to figure out what the reasons are behind a behaviour but I really believe some behaviours come from nowhere. For yours it was just a childish thought that grew and became an obsession and trying to find the root of it might not be the only way to conquer it. You've shown you have massive strength by quitting drink so you just need to figure out a way to believe in your control over your body. Have you ever tried not stopping and carrying on ie playing the guitar? If so what happens? If not you should try it. Best case scenario nothing happens and you realise you DO have control. Worst case scenario you change your pants.
Ps sorry for the essay... I've never replied to a post before :/
(If I don't spellcheck I'm one step closer)